1. Field of the Invention
The present invention relates to a network system, especially to a route change method based on a delay time for transferring a packet.
2. Description of the Related Art
To realize an economical packet network with little drop in the throughput that effectively uses network resources where routing reflecting an actual traffic state is performed without the need for any revision to relay routers, Japanese Unexamined Patent Application Publication No. 2002-044125 discloses a packet network where an incoming edge side router placed at an input side of a network and an outgoing edge side router installed at an output side transmit/receive a test packet with each other or give a time stamp to an IP (Internet Protocol) packet including user information so as to measure an actual round trip delay time or propagation delay time in each route. A route for transmitting a packet is selected according to the result of the measurement. It also discloses a technique for smoothing and using a plurality of measurement results.
To prevent line congestion by devising load distribution in a data exchange network and effective utilization of bypass lines with respect to the route selection system in the network, Japanese Unexamined Patent Application Publication No. H09-191322 discloses a data exchange route selection system. Each station of the data exchange network is provided with a delay time measurement means measuring a delay time of each route, a line utilizing rate measurement means measuring a line operating rate for each route and a delay allowable value setting means setting an allowable delay time between each terminal equipment under the control and an opposite terminal equipment. Then a route satisfying an allowable delay time of the terminal equipment among plural routes is selected for each communication and a route with a lower line operating rate is selected among the selected routes to average the line operating rate while keeping the response of the terminal equipment.